This invention pertains to direct access disk storage devices and more particularly to a format and mode of operation that enables all sector ID fields in a cylinder to be read in a single revolution.
A disk file is most commonly operated in a physical mode wherein a track is read continuously sector by sector in sequence. A second mode of operation is a logical mode wherein the sectors within a cylinder are staggered in a mount l/n of a sector wherein N is the number of tracks forming the cylinder. By writing one sector and thereafter switching to the head which will encounter the sector spaced l/n sectors from the terminal end of such one sector, successive sectors may be written in a manner which permits the intersector gap to be reduced in length. This derives from the ability to switch from writing (in the data sector portion) to the reading of the next subsequent ID sector portion without having to enlarge the gap between such sector portions to accommodate the write signal decay. This procedure produces the maximum data rate which accommodates both write and read functions.